Reflector



Sept. 10, 1935..

w. G. wcSon REFLECTOR Filed March 6, 1933 3 Sheets-Sheet l /INVENTOR. mm-Mm 10M AT ToRNEY f W. G. WOOD Sept. 10, 1935.

REFLECTOR Filed March 6, 1933 3 Sheets-Sheet 2 I N VEN TOR.

. f ATTORNEYS.

Sept. 10, 1935.

W. G. WOOD REFLECTOR Filed March 6, 1955 3 Sheets-Sheet 3 INVENTOR.

ATTORRI W Patented Sept. 10, 1935 NETED STATES PATENT OFFIQE te American Woodlite cisco, Calif., a. corporati Corporation, San Franen of California Application March 6, 1933, Serial No. 659,670 14 Claims. (01. 240-4137) This invention relates to reflectors for beam projection as typified by vehicular head lamps and a given distribution of light or an illuminated area of a predetermined pattern is desired and to obtain which a special form of reflector is required.

The object of the invention is to project a reflected beam having wide horizontal but limited vertical spread and other desirable characteristics of distribution without relying on the use of refracting lenses.

A further object is to project the forward or axial rays in a concentrated beam, the concentration diminishing as the direction departs horizontally from the said axial position until the beam is diffused in vertical distribution in a direction approaching right angles to the axial direction. In other words, the beam desired will spread approximately 180 degrees in the horizontal plane of the reflector, and will have a vertical distribution of three degrees more or less in the forward direction and forty-five degrees more or less at the side wings of the horizontal spread.

This light distribution is desirable in certain forms of beam projection, particularly vehicular road lighting. The forward lighting should be of a high intensity for aid in discerning distant objects in the roadway. Tins intense distribution could be carried around in the horizontal plane; the illumination requirements at the sides of the road, however, require rather dispersed field for a more complete visibility.

A further object is to obtain a reflector, the dies for which can be generated mechanically to insure uniformly smooth surfaces.

A further object is to obtain a reflector whose forward walls converge to a narrow front opening or aperture to restrict the apparent size of the beam projector.

A further object is to obtain a form, the lower half of winch may be used in connection with a hemiellipsoidal upper half to produce a beam lyin below a horizontal plane through the principal focus for the purpose of eliminating glare.

This invention is a further improvement over my earlier patents numbered 1,819,725 and 1,819,726, in which I disclose forms of reflecting surfaces which are elliptic arcs in approximately horizontal sections and. arcs of conic sections in vertical planes passing through an axis located in the forward portion of the reflector. In these earlier inventions, the rays of the reflected beam lie in planes of a horizontal pencil of planes and condense or focus on a single horizontal locus line of remote foci.

This invention departs from my earlier ones by evolving a form which has a plurality of secondary foci vertically distributed within the reflector form and other loci of remote foci which are two hyperbolic arcs lying in the horizontal 6 plane. This specification discloses such a structure. It has the physical properties of: reflecting beam rays convergingly toward a distant locus in the center of the field; then as the direction departs laterally from the central or axial posi-- 10 tion, the said distance foci become more and more remote until it is at an infinite distance and the beam rays are parallel; further departure from the central direction causes a reverse focal effect, the beams reflected rays diverging as though origl5 inating on the other hyperbolic focal arc.

It is to be understood that this invention is concerned only with the form of the reflector, which is intended to be pressed to this shape, polished and mirrored, furnished with a light source and a light emitting aperture and a suitable housing, in any conventional manner. Consequently this invention is best described mathematically and physically in its elemental form, for which explanation I have appended several views thereof.

For the purposes of explanation, in Figs. 1, 2, and 3 only one-half of the geometric form is shown, there being a similar half on the opposite side of the median vertical longitudinal plane to complete the figure. However, either half acts as a unit and may be positioned in such a manner with respect to the other half that the beams, produced from a single light source, will overlap to intensify a central area as shown in Figs. 4, 5, and 6; or deflect downwardly at the sides to i1- luminate nearby ground surfaces as shown in Fig.

7, or otherwise as may be desired.

In the drawings:

Fig. l is a vertical longitudinal section of my invention taken on the central plane.

Fig. 2 is a plan view of the right half of the reflectors form and shows the projection of the light rays from the said right half into the lefthand field, a feature of my invention.

Fig. 3 is a front view of one-half of the reflector form, further modified by the substitution of the quarter segment of a hermi -ellipsoid in place of the top portion of the geometrical figure of my invention.

Fig. 4 is a plan view showing two reflector portions positioned with a single principal focus but with a horizontal angular lateral displacement about a vertical axis at the principal focus to give overlapping central beams.

Fig. 5 is a front view of the combination shown in Fig. 4.

Fig. 6 is a representation of the light pattern obtained from that arrangement.

Fig. 7 is the rear View of a combination of two reflector forms wherein a ve cal angcdar displacement, about the horizontal axis, separates two component reflector forms for the purpose of giving downwardly depressed side beams.

Fig. 8 shows the light pattern obtained by the simple combination of two component reflector forms which are joined on their central vertical planes.

Fig. 9 is a central vertical transverse section of the reflector showing the pattern of light beam projected when the halves have been di. aced both in the manner illustrate in Fig. 4 and in the manner illustrated in Fig. 5; and

10 is a diagrammatic view of the reflector form in plan. illustrating the scope of projection of the light beam in a horizontal plane.

The generation. of my reflector surface is clearly shown in Figs. 1, 2, and 3. The complete lateral surface is shown at 4-'i-5-54 of Fig. 1, 6-8-5-4-5 of Fig. 2 and 4-lEl-5-54 of Fig. 3, and is generally designated by the letter R. E1 is its rearward vertical profile, being an elliptic are having its principal focus at (l and its remote conjugate focus at Hi its forward vertical profile, a hyperbolic heating a principal focus at .2 and conjugate focus at The master prolate ellipsoid of revolution erally designated by the letter M is indi ated by its projections in the three views. It has one focus at 5 and a conjugate focus at i. From the principles of optics it is known tha light, diverging from a source at will be reflected from ellipsoid M, to converge through its conjugate focus i. The horizontal major ellipse of this master ellipsoid is the form about which any reflecting surface is generated.

Having selected the remote point 3 to which I desire to project rays from the rearward p ile, and the nearby point 2, on lines from wl desire to reflect rays from the forward profile, I lay out the two opposite cusps of the hyperbole. 3-i5 and 2-H, Fig. 2, in the central horizontal plane containing ellipse 'E-lli-'i and having feel at l and 35 determined by the relative positions of points a, l, and ii and ellipsoid M. Maintaining a constant principal focus at l? and remote tool at consecutive positions along the arc 3-i5 I first develop prolate ellipsoids of revolution having said focal points and tangential contact with said master ellipsoid M. One such ellipsoid is designated as E2 with tool at It contacts the master ellipsoid M at which is on the line l5-I produced. As will be later explained, it also passes through the points 4 and 5, which are also the intersections of the principal ellipse E1 and the hyperbole. iii (F 1). This ellipsoid E2 provides one element of y reflector. It is the arc iii-5, Figs. 1 2, which is an ellipse with major axis 56-4! and contains points and 5. This ellipse is also the intersection of the ellipsoid E2, with the right crcular cone whose axis l5-i8 is tangent to the hyperbola L -i5 at it and has one element 55-4. Light rays from 8 which strike the arc ltare reflected by said element and since .?i--5 lies on ellipsoid E2, the rays refocus at 55 according to the law of reflection, crossing the central vertical plane 6-4-5 along an elliptic are, hetween i and 5, which is the intersection of right circular cone and the said central vertical plane. The plane containing said element 5 is vertical because it is the litersection two confocal quadric surfaces of revolution (el and cone), whose axes lie in the central Zontal plane 6-lt3. Since point is any 5 point on hyperbole 3--lii, it follows reflecting elements of my inven' elliptic arcs, having proximate the horizontal section of the l I at the point of tangency 'n (5'!) on the horizontal trace ellipsoid (E2) where it plane containing said prox'ina... points 4 and 5.

As point l5 moves consecutively o. hyperoola the lengt i the generating ellipsoid E2 llw infinitely long, namely, to t c hyperbole meets its asymptote position the major axis of s lies in the line which asymptote t: and ti surface of revolution E: o 1 P. This surface provides the reflecting lF.'2C'flu lit-5. It reflects rays to infinity; hence, said rays -35 are parallel. Two of rays are f. 5-42 After point l5 has reached the asymptote li-l3 it is made to fall on the opposite cusp of the hyperbola, viz., 2-Hl, the eccentricity of the 30 generating quadric surface of revolution becomes greater than un ty and of hro rzol The ta lal element used in my 1 then a hyperbolic arc. The hype holofd v;lio-= trace is shown at Hz is typical. proxim: focus is 9, it is tangent to the master cllipsci M at 9 and its remote focus lies e tion of the line l&, extended, i 2-4 When the remote focus on same distance from 5 that 5 is f crating surface becomes the er whose trace is shown at iii-55 in F Heretofore, the generating surface has been concave with respect to 6. From !2 to "I these generating surfaces become convex with respect to 0 and at l have the limiting form 4-1-5 or Hi, the vertical hyperbola with proximate focus at 2 and remote focus at 0.

Typical reflected rays are shown in the three Figures 1, 2, and 3. In Fig. l ray 22-30 con- 50 verges to focus 3 while ray 8l23 is divergent as if coming from 2. In Fig. 2 rays 25 and 25 are convergent to 3, rays 23 and 24 are parallel and rays 2! and 22 are divergent from a remote focus on 2-l4, depending on the species of the gencrating quadric surface; that producing rays 7.5, 25 being ellipsoidal, that producing 23, '24 being paraboloidal and that producing 2|, 22 being hyperboloidal.

In Fig. 3 ray 33 converges toward the central horizontal plane ill-Ei-l, hence its generating surface was an ellipsoid, while ray 34 diverges from the horizontal plane, hence its generating surface was a hyperboloid. Any degree of convergence of forwardly emitted rays and divergence Q5 of lateral rays can be obtained by the proper choice of the vertices, 3 and 2, of the hyperbolic loci together with the inclination of the asymptote Ill-l3.

By a similar construction the opposite half of my reflecting surface can be generated using the opposite halves of the cusps of the hyperbolic focal loci. To permit the projection of light from the reflecting surface, I remove the forward portion thereof. While it is theoretically possi- 7 5 I the gen- 40 plane J -ble to obtain 180 of spread of emergent rays by cutting away the portion forward of the arc 9-5, such construction is not mechanically desirable and I show my reflector terminated on a vertical plane, normal to the axis through forward focus i. This gives rise to the curve 98 in Figs. 1, 2, and 3. Other positions however may be desirable.

In Figs. 1 and 3 I show the utilization of the lower half only of this reflecting surface, substituting therefor, above the principal horizontal plane, one-half of the master ellipsoid M. This substitution makes it possible to project all reflected rays below the horizontal plane as for example ray 3 i-32, in order to eliminate glare in vehicular head lamps. The forward position of this portion of the master ellipsoid would be cut away on the same plane or curve of the lower reflecting surface for constructional considerations.

Having thus described the generation of the elemental figure of my invention, I will disclose the methods of combining the elements to obtain specific light distribution benefits. While two symmetrical halves may be combined along their median planes through 6-5 as I show in Fig. 8, I may spread the said median planes, maintaining the principal foci 6 of two halves coincident. In Figs. 4 and 5 the spread is horizontal, each being turned outward through an angle S. In these figures, the subscript letters a and b are used to denote points pertaining to the right and left reflector halves respectively. The generating surfaces of revolution for the right half follow the hyperbolic cusps 3al 5a and 2a-I do, while those for the left half follow the cusps Bb-ifib and tb l ib. The remote foci duplicate in the zone 3a-3b to give double intensity to the projected light, as for example ray 25a from Ra and 25b from Rb. While the cusps Za-Ma and 2bl 5b are shown separated by the interval 2a2b, these portions refer to generating hyperboloids forward of the aperture through Elm-9b and are used merely to govern the contour of the reflector forward of points lGa and l9b. The two last mentioned are the points at which horizontal rays must be reflected to follow the asymptotes iia-i3a and Hbl3b respectively. The angular spread between rays 23a and 23b designates the zone in which the rays converge in vertical direction. The zone rearward of rays 23a and 23b is characterized by spreading or diffusing rays giving the dispersed lateral beam characteristic of my invention.

While in Figs. 4 and 5 I show at 36 an overlap of two surfaces due to the revolution of reflectors Ru and Rb about a common vertical axis through 9, actually but one surface is used, the median vertical plane through 0 terminating the two surfaces.

At 3'5, Fig. 5, I show a reflecting filler section in the angular space between the two reflector halves, viz., la-ib in Fig. 4. This will preferably be a quadric surface having a principal focus at Q, and containing the arcs 6a-5a and 6b-5b.

In Fig. 6 I show the overlapping light fields, obtained from the form of Figs. 4 and 5, the rear elevation of the reflector being shown at Ma, Mb, Ra, and Rb. The light field from 38a to 39a is produced by reflector Ra while the field from to 3% is produced by reflector Rb. The overlapping fields from 38a to 38b are zones of doubled intensity. Rays 3-4! and :32 53 illustrate rays which are spreading from a hyperbolic element, while rays 57 and 53 are converging from an elliptic element.

In Fig. 7 I show a vertical angular displacement of the median planes of reflectors Ra and Rb, said angle being 214. This gives rise to the depressed fields 59a and 5912, the angle t being the angle of depression and equal to u. Rays 5 4445 and 4l48 illustrate the characteristics of the arrangement. The zone 49-49 indicates overlap in the central field. The reflector is shown in rear elevation. Either the hemiellipsoid M or the top edges of the lower re- 10 flector Re and Rb must be reduced by the angle Eu, whereas a reflecting filler section 46 equal in angularity to la would be supplied between the two' median edges of reflectors Ra and Rb. Points 5c and 5d are the lower apices of these reflector halves.

In Fig. 8 I show the light field 5l5253 projected from a simple combination of two reflectors, Ra and Rb, joined along their median vertical planes, i. e., 6-5. Said light field is seen to be narrow vertically in the center and becomes wider at the sides. Rays 55-54 and 56-57 are typical.

By combining the horizontal angular spread of the reflector and beam shown in Fig. 6 with the vertical spread of Fig. 7, a single reflector form may be constructed having strong central illumination and depressed and diflused lateral wing-beams. Such a light pattern is characterized in Fig. 9 where the reflector shown is one constructed according to my invention and having both the horizontal spread illustrated in Fig. 6 and the vertical spread illustrated in Fig. 7. In this view a source of light or electric lamp B is shown in dotted lines and is to be understood to be positioned at the focus 0 of the reflector. In Fig. 10 the reflector of Fig. 9 and the light beam projected by it are illustrated in plan showing the wide spread of the beam and the relatively narrow central portion of double intensity.

For purposes of manufacture of said reflectors,

I contemplate combining the lower and upper members thereof in an appropriate manner, providing a suitable light source at 0, and a lightemitting aperture at 8-9, and mounting the said reflectors in a holding case suitable tothe specific use for which it is to serve.

Having thus described my invention, what I claim and desire to secure by Letters Patent is- 1. A reflecting surface for beam projectors which is elliptic on its horizontal plane of symmetry, whose vertical rearward profile is an ellipse having one focus coincident with one focus of the horizontal ellipse, the other focus being at a. remote forward point, whose vertical forward profile is a hyperbolic arc with a remote focus coincident with the focus common to the said horizontal and vertical ellipses, its proximate focus lying forward of but adjacent to said reflector, two points exterior to said reflector through which said vertical conic sections pass and circumferential walls which are elements of quadric surfaces of revolution having one focus common to all elements, the other foci lying consecutively along the arcs of a hyperbola of two cusps, said surfaces being tangent to the principal horizontal ellipse and containing the said two exterior points.

2. A reflecting surface for beam projectors which is the inner envelope generated by a family of quadric surfaces of revolution having a principal fixed focus, said family being disposed about a common axis through the lata recta, the remote foci thereof following a complete hyperbola of two cusps whose plane contains the said fixed -focus, said quadric surfaces having a point outside the axial plane of rotation common to all members of said family.

3. A reflecting surface for beam projectors having a principal focus and a body portion which is the inner envelope of a family of confocal quadric surfaces of revolution which are disposed about a common vertical axis through said principal focus, maintaining tangency to a master ellipse on the principal horizontal plane and passing through each of a symmetrically positioned pair of points external to said horizontal plane and forward of said master ellipse.

4. A reflecting surface for beam projectors having a principal focus and having a form which is elliptical on a horizontal plane through said focus and which is the inner envelope generated by a family of quadric surfaces of revolution which rotate about a latus rectum through said principal focus, the outer foci following the arcs of hyper-bolas whose axial intersections are forward of said master ellipse, said quadric surfaces being selected to contain a common point exterior to the plane of the horizontal ellipse.

5. A reflecting surface for beam projectors which is the envelope of all quadric surfaces of revolution tangenting a master horizontal ellipse and having conjugate foci one of which lies at one focus of said master ellipse, the other foci falling upon the arcs of a pair of coaxial confocal hyperbolas whose center and axial intersections are in the plane of but forward of said master ellipse.

6. The reflector form for beam projectors which is elliptic on its median horizontal plane, whose forward and rearward vertical longitudinal profiles are conic sections each having one focus in common with the median horizontal ellipse, the other respective foci being separated but lying on the median central axis, the remote focus for the rearward conic section being forward of the second focus of the said forward conic section, said conic sections intersecting at a point exterior to the plane of said median horizontal ellipse, the lateral walls of said reflector form being elements of quadric surfaces of revolution having a common focus at the said principal focus, axes which lie in said median horizontal plane and which surfaces contain the said exterior point.

7. A reflecting surface formed by consecutive vertical arcs of the second degree which are the intersections of a family of quadric surfaces of revolution with a family of right circular cones, said quadric surfaces having a common principal focus, axes lying in the horizontal plane, remote foci of said quadric surfaces and apices of said right circular cones being consecutively coincident and following the cusps of two coaxial confocal hyperbolic arcs, the axis of each said cone being tangent to its hyperbole, a horizontal element thereof passing through a common point within said reflector but forward of said principal focus.

8. A reflecting surface whose portion below the principal horizontal plane is the same as the lower half of the form described in claim 1, whose surface above the horizontal plane is a hemiprolate ellipsoid, having a focus coincident with said principal focus, and lying over and adjacent to the said lower portion.

9. A reflecting surface composed of two symmetrical reflector portions generated as set forth in claim 1, which are combined with a common principal focus but whose median vertical planes are angularly displaced by spreading, forward of said principal focus, the opening thus formed being closed with a reflecting surface.

10. A reflecting surface composed of two component halves generated as set forth in claim 1, which are combined at a common principal focus, whose vertical median planes are displaced angularly by spreading below the principal focus, the

opening thus formed being closed with a reflecting surface conforming to the vertical profiles thereof.

11. A light projector comprising a reflecting surface which is the envelope of arcs selected from quadric surfaces of revolution at their point of tangency with an ellipse in a horizontal plane.

one of the foci of said quadric surfaces being commen and the other foci of said quadric surfaces progressing along given hyperbolic arcs, and a source of light at said common focal point whereby the reflected beam will have a wide horizontal spread and a vertical spread relatively narrow in a forward direction and increasing in width toward the outward extremities of the horizontal spread.

12. A light projector including a source of light and a reflecting surface, said reflecting surface comprising the envelope of a family of quadric surfaces of revolution having a common focus at which said light source may be positioned and other foci lying along given hyperbolic arcs in a horizontal plane remote from the reflector to create a beam having a wide horizontal spread and a vertical spread relatively narrow in a forward direction and increasing in width toward the outward extremities of the horizontal spread.

13. A reflecting surface having a principal focus, a master ellipse on its central horizontal plane, a fixed external point lying in the central vertical plane, forward of any point in said master ellipse, conjugate horizontal hyperbolas whose vertices lie in the major axis, extended, of said master ellipse, and having side walls defined as being the envelope generated by vertical conicsection arcs whose vertices lie on the master ellipse, pass through said external point and represent the intersections of planes with right circular cones whose vertices lie on, and whose axes are tangent to, consecutive positions on the hyperbolic arcs.

14. A reflector for producing a light pattern relatively narrow and intense at the center and increasing in width and decreasing in intensity toward its outer extremities comprising elliptic, parabolic and hyperbolic sections to reflect light from a common source, the elliptic sections directing the light centrally, the hyperbolic sections directing the light toward the outer extremities of the pattern and the parabolic sections directing the light intermediate the center and outer extremities of the pattern, said reflector being formed in angularly related halves to produce double intensity at the central portion of the pattern and to cause the outer extremities of the pattern to incline downwardly.

WILLIAM G. WOOD. 7 

